1. Field of the Invention
This invention relates to a novel epoxy resin aqueous paint composition and, in particular, to a novel epoxy resin aqueous paint composition which contains a special amide as a hardening agent to improve the rust preventive, anticorrosive and weatherproof properties.
2. Description of the Prior Art
Paints are usually prepared by dispersing a synthetic resin, a coloring agent and other auxiliary additives in an organic solvent. Since organic solvents are defective from the standpoint of sanitation, safety and air pollution in that they are toxic to the human body, inflammable in operation, easily cause fire and explosion and the like, it is highly desired to develop non-polluting and safe paints, for example, of an aqueous solution type, a non-solvent type or the like. In particular, development of aqueous paints of the room-temperature hardening type, i.e., those capable of being hardened at a temperature in the range of about 15.degree. to 30.degree.C for a period of about 6 to 24 hours, that are easily applicable for large structures such as vessels or bridges for which heat treatment is impossible.
Epoxy resin aqueous dispersions which do not contain any organic solvent are known and include a mixed aqueous emulsion of an epoxy resin and a polymeric polyamide, which is prepared by mixing in an aqueous medium an organic solvent solution of an epoxy resin with a condensation product of an aliphatic polyamine and a polycarboxylic fatty acid in the presence of a water-soluble organic carboxylic acid (as disclosed in U.S. Pat. No. 2,899,397), those which contain as a hardening agent an addition product of an aliphatic or aromatic monoepoxide and an aminoamide prepared from a fatty acid and an alkylenepolyamine (as disclosed in British Pat. No. 1,242,783). The use of these special hardening agents can provide coating compositions, e.g., paints which harden at room temperature and form films having excellent strength and water resistance properties. However, when such aqueous paints are coated on the surface of a metal, particularly steel, their rust preventive and anticorrosive properties are not sufficient, and the coated film has poor adhesion on immersion in fresh water or salt water. Therefore, these aqueous paints are not suitable at all for metal coating. Thus, epoxy resin paints of the room-temperature hardening type which are capable of being diluted with water and suitable for metal coating are thus far unknown.